Industrial swinging doors are adapted to enclose doorways in industrial or commercial facilities and are normally intended to be opened by the impact of moving material handling equipment, such as fork lift trucks. As the door is subjected to considerable impact by the material handling equipment, the doors should be lightweight, as well as impact and abrasion resistant.
In the past, industrial doors have been composed of a structural steel or rubber frame with abrasion resistant plastic or rubber facing sheets connected to the frame. However, doors of this type are of a relatively heavy and expensive construction and are prone to delamination.
Industrial doors constructed primarily of plastic and/or rubber materials tend to warp significantly in applications where a temperature differential exists, such as in freezer or cooler applications, due to their high coefficient of thermal expansion.
U.S. Pat. No. 4,084,347 discloses an industrial door formed of lightweight plastic materials. As is disclosed in this patent, the door is composed of a hollow body of a moldable plastic material and the interior of the body is filled with an insulating material, such as foam plastics, or the like. In addition, the industrial door of the aforementioned patent includes a plurality of reinforcing rods which are embedded within the insulating material and extend the height of the door.
In the past, honeycomb panels formed of paper or thermoplstic resin have been used in the manufacture of residential doors and furniture. In products of this type, facing sheets of plywood, metal foil, plastic and the like are bonded to opposite faces of the honeycomb core. However, constructions of this type are not satisfactory for high impact applications, such as industrial doors.